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BY- SAURABH KUMAR MEENAMECHANICAL ENGG(7TH SEM)

REG. NO-2010UME226

MNIT JAIPUR

DATE-25/09/2013

SEMINAR

ONCONTINUOUSLY VARIABLE TRANSMISSION (CVT)

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Basics of t ransm iss ion

The job of the transmissionis to change the speed ratiobetween the engine and thewheels of an automobile.

The transmission uses arange of gears to make moreeffective use of the engine'storque as driving conditions

change.

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PROBLEMS WITH MANUAL & AUTOMATIC TRANSMISSI

The traffic condition has become

annoying in our big cities.

In such a case will automatics

transmission make sense to theIndian customer.

But conventional automatics

always consume slightly more fuelthan manual transmission and the

lack of sophisticated automatics.

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Today automobiles use either a conventional manual orautomatic transmission with multiple planetary gear setsthat use clutches to achieve discrete gear ratios .

The continuously variable transmission replaces discretegear ratios with infinitely adjustable gearing through oneof several basic CVT designs

Introduction of CVT

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Overv iew of a CVT:

Varies the transmission ratio continuously

Shifts automatically with an infinite number ofratios.

Seamless power delivery

Constantly changes its gear ratio to optimizeengine efficiency

Allows the engine to rev almost immediatelyto deliver maximum torque

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Components of

CVT

1.A variableinput driving pulley

2.An output(driven) pulley

3.A metal belt/rollers

4.Sensors and microprocessors

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Working principle

A pair of variable-diameter pulleys, each shaped like a pair ofopposing cones, with a metal belt or chain running between them.

One pulley is connected to the engine (input shaft), the other tothe drive wheels (output shaft)

as the pulley halves come closer together the belt is forced toride higher on the pulley, effectively making the pulley's diameter

larger.

Changing the diameter of the pulleys varies the transmission'sratio.

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HOW CVT WORKS?

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Types o f CVT

Metal Push Belt CVT.

Toroidal Drive CVT.

Variable Diameter Elastomer Belt CVT

Nutating Traction Drive CVT

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Simulation of CVT

Push Bel t

This belt transmits power betweentwo conical pulleys, or sheaves, onefixed and one movable .

A sensor reads the engine output andthen electronically increases ordecreases the distancebetween pulleys, and thus the tension

of the drive belt

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Toroid al Tractio n Drive CVT:

Uses rollers to transmit torque between the inputdisc and output disc.A viscous fluid transmits torque between rollers anddiscs.

Rollers and discs never touch.

The angle of the rollers changes relative to shaftposition resulting in a change in gear ratio.

The change in angle by a roller must be mirrored bythe opposing roller.

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Toroidal CVT

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ADVANTAGESDecreases engine fatigue

infinite number of gear ratios,maintaining the engine in its optimum powerrange

More mechanically efficient than Automatictransmissions.

Greater fuel efficiency than both manual andautomatic transmissions.(Fuel savings of more

than 17%).

Smooth, responsive and quiet to drive

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CVT Vs. Manual Transm issio n

Theoretical comparison under ideal

conditions

1991 FIAT UNO

M=1250 KG,TORQUE=101.2 NM

0-100 KMPHMT-11.9 SEC /CVT-8.8 SEC

CVT proved 35% more

efficient than the MT.

With same car andengine, the CVT takesonly 75% of the time toaccelerate to 100km/h,

compared to the MT.

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DRAWBACKSLimited torque capacity when comparedto manual transmissions.

Additional gear train required for reverse

conditon.

Larger and more costly than manual

transmissions.

Unwillingness to discard billions ofdollars in development in MT & ATs.

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The IC engine is nearing both perfection andobsolescence; advancements in fuel economy andemissions have effectively stalled.

CVTs could potentially allow IC vehicles to meet thefirst wave of new fuel regulations

Costs will be reduced further and performance willcontinue to increase.

Ultimately it will give CVTs a solid foundation in theworlds automotive infrastructure.

Future of CVT

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THANKyou